The present invention relates to an adjustable bridge that is used to raise or lower all of the strings on a stringed instrument at the same time relative to the instrument frets even when the strings are under tension from tuning.
Sound production from stringed instruments is almost always accomplished in one of two ways. In the first case, at least one microphone type sensor is used to pick up string vibrations electrically where these electrical vibrations can then be amplified electrically. An electric guitar exemplifies this first case. In the second case, a vibratory sound path is provided that originates with the vibrating strings, passing through a bridge supporting the strings to the top surface of a hollow sound box which amplifies the vibrations mechanically. Acoustic instruments such as guitars, mandolins and violins exemplify this second case. The two cases present different structural limitations for adjustable bridges, because in the first case, little concern has to be given to providing a vibratory sound path between the strings and a sound box. Acoustic instruments require a bridge which does not inhibit this sound path.
In both types of musical instruments, bridges are important in setting the distance of the strings over the instrument fret-board. Adjusting the height of the strings above the fret-board is important for the playability of the instrument, and to prevent string buzzing.
Adjustable bridges having screw adjustments have often been used in the past to adjust the string height above the instrument fret-board, as shown in U.S. Pat. No. 4,248,126 or U.S. Pat. No. 4,334,454. Both of these patents show adjustable bridges for use with electric guitars.
U.S. Pat. No. 5,600,078 shows another adjustable bridge for use with an electrical guitar where an adjustable member slides up an inclined plane to adjust the string height of an individual string.
A need exists for an adjustable bridge for use with a stringed acoustic instrument, where the sound produced by the strings is transmitted through the bridge to the top surface of the sound box. Such bridge needs to have the capability of easily adjusting the height of all the strings over the fret-board at the same time, while the instrument strings are under tension.